Try getting the latest driver from the manufacturers website. If that is the driver you are using i would try a version before. Also you could go into your device management and delete all the USB serial bus controllers there. Once Complete right click on the name of the computer at the top of the tree and scan for hardware changes this will set them back up if it has not done it automatically. This might clear up some of your USB issues.
Just a few Ideas.
Where does one find the "Device Manager" on Windows XP?